Roman Medicine is a very complex issue and deeply studied: its complexity however derives by different interrelated problematic dimensions. Medicine was not only a technical or scientific (or pseudo-scientific according to some researchers and scholars) topic (see for example the rather advanced methodologies and practices Romans adopted in surgery): medicine implied a deep knowledge of Nature, its cycles and manifestations in a very broad sense (i.e. with regards to the sphere of the plants' and trees' world) and the involvement of Divine Forces.
Here is not possible analyze in detail this issue and I will suggest in the future some specific books devote to this. Now I'd like to highlight just a few interesting expressions of the Divine presence in the Roman Medicine.
In the incantamenta, the doctor invokes Mother Earth so that She will give power to the herbs he needs to prepare his medical remedies. Then he invokes the herbs so that they let him pick up them confirming that he obtained the permission to collect them by Who created them. He invokes the herbs so that they will produce the positive effects he needs. If everything has gone well with positive results, the doctor will thank per nomen Eius qui uos iussit nascier (in the name of who has created you).
In an interesting book titled "La Preghiera Romana (the Roman Prayer)" by G.B. Pighi (in italian) are cited some beautiful invocations:
Herba uettonica, quae prima inuenta est ab Scolapio, his precibus adesto, peto; magna herbarum pmnium diceris per Hunc, qui te iussit creari et remediis plurimi adesse.
"Betony, who first was discovered by Aesculapius, I pray, may you attend these prayers; of all the herbs will you be called great for this, that he has command you to be created and many remedies to offer.
Herba eriphia, ut adsis me rogante et cum gaudio uirtus tua praesto sit et ea omnia persanes quae Scolapius aut Chiron centauros magister medicinae da te adinuenit.
"Herb Eriphia, come to my begging and may your glad powers be close at hand, and by her, who Aesculapius or else the centaur Chiron, the great doctor of medicine, discovered in you, will all be most healthy."
Sancta herba chrysocanthos, per Scolapium, herbarum inuentorem, te rogo, ut uenias huc ad me hilaris cum effectu magno et praestes quae a te fidius posco.
"Holy herb Chrysocanthus, among the herbs discovered by Asculapius, I ask that you may come cheerfully hither to me, with great effect, and excel in what I ask of you in good faith."